Electrical busway distribution systems, or busway systems, that are designed for outdoor use need to be weatherproofed or protected from the elements such as moisture, rain, or snow. Busway systems that are employed indoors also have to be protected to a certain extent from water penetration from various sources such as dripping water or sprayed water. The ingress and diffusion of water and/or moisture into a busway system can cause shorting among the various separate phased bus conductors, leading to potentially catastrophic problems such as fires.
The traditional method of sealing joints or gaps in busway housing assemblies or covers has been the use of gaskets or sealing strips to weatherproof the busway systems. U.S. Pat. No. 4,979,906 entitled "Busway Weatherproof Housing" protects outdoor busway systems from exposure with an improved weatherproofed housing for the busway joints. The housing includes end pieces which are attached to and sealed to the busway enclosure that houses and protects the electrical conductors, and joint covers enclosing the joint area between the end pieces. Sealing the inside surface of the joint cover and the outside surface of the joint end piece is accomplished by compressing a rubber material between the two surfaces.
U.S. Pat. No. 5,401,906 entitled "Water Resistant Supplementary Joint Cover for an Electrical Busway" describes the use of gaskets and sealing strips to waterproof busway systems. In this patent, a joint cover system is disclosed. The busway system comes with supplementary water dams and joint covers to protect the busway joint area from the ingress of occasional dripping or sprayed water from within a building. The dam assembly comprises sealing plates and sealing strips made out of a tacky, deformable nonelastic material such as rubber. The joint cover system further includes connecting channels with water resistant gaskets attached. The gaskets seal the busway housing sides and the cover plates against the ingress of water.
Besides the above approaches which require pre-fabricated and customized sealing strips or gaskets sized to fit between or around joints and cover parts, there exists another method to close the joints, gaps, or surfaces in busway housing assemblies without the need for multi-pieces of gaskets and sealing strips. This method employs polysulfide as a sealant to seal the joints and gaps in busway systems. There are various disadvantages associated with this method. The use of polysulfide as a sealant is a cumbersome method, requiring the application of a surface adhesion-promoter or a primer to the joint surfaces first to cause the polysulfide to form an intimate contact and maximum bond with the joint surfaces. Additionally, polysulfide is a two-component system requiring a cumbersome and complex mixing process along with a complex mixing ratio prior to application. The mixing process is more often than not a trial-and-error run to obtain the optimum mixing ratio in order to give a sealant that is strong and adhesive. If the mixing ratio is not exact to give an optimum result, the sealant has to be scraped off the busway and the entire batch of sealant material is scrapped. This polysulfide sealing process typically results in a material waste of up to fifty percent (50%) or more.
Polysulfide sealant takes a long time to "fully" cure as applied on busway systems. The drying time is about twenty minutes to touch, forty minutes or so to set, and about seven days for a final cure. In addition, the material often cures in the delivery system and plugs up the line and the application gun. This means the delivery system has to be shut down for purges, resulting in frequent downtime and material loss due to the clean-up. Furthermore, polysulfide is a health and environment problem with the polysulfide material having an obnoxious odor and a high hazard rating due to the required presence of a lead dioxide curing agent.